Forging device and forging method

ABSTRACT

In a forging device including a rotating table and a shaping roller, which forging device forges a workpiece such that an outer peripheral surface of the shaping roller is pressed against an end surface of the workpiece in a central-axis direction of the workpiece while the workpiece is rotated by the rotating table, the shaping roller is placed apart from a rotation axis, and a position of that end of the outer peripheral surface of the shaping roller which is opposite to a rotation-axis side in a central-axis direction of the shaping roller is placed at an outer side in a radial direction of the workpiece relative to a position of an outer peripheral surface of the workpiece that has been forged.

TECHNICAL FIELD

The present invention relates to a forging device and a forging methodeach of which performs molding such that a shaping roller is pressedagainst a workpiece so as to expand the workpiece in a radial directionand a central-axis direction of the workpiece.

BACKGROUND ART

Patent Document 1 describes a forging method for performing diameterexpansion molding to expand a cylindrical metal workpiece in a radialdirection of the workpiece. In the forging method of Patent Document 1,the workpiece is rotated around a central axis of the workpiece, and acylindrical shaping roller is pressed against that end surface of theworkpiece thus rotated which is on one side in a central-axis directionof the workpiece. The shaping roller makes contact with the workpiece assuch, and then, the shaping roller is moved down with the shaping rollerbeing rotated with the workpiece. Hereby, a pressure is applied to theworkpiece from the shaping roller, so that the workpiece can be expandedin the radial direction.

CITATION LIST Patent Documents

Patent Document 1: Japanese Patent Application Publication No.2011-224605 (JP 2011-224605 A)

SUMMARY OF THE INVENTION Problem to be Solved by the Invention

However, in the forging method of Patent Document 1, although it ispossible to perform diameter expansion molding to expand the workpiecein the radial direction of the workpiece, it is difficult to performboss molding to form a boss portion formed by raising a central part ofthe workpiece in the central-axis direction of the workpiece. In view ofthis, it is necessary to separately perform a step of performing theboss molding after a step of performing diameter expansion molding isperformed first by the forging method of Patent Document 1. Accordingly,different forging devices are required for respective steps at the timewhen a forging having a boss portion is manufactured, which increasescost.

In view of this, the present invention has been accomplished in order tosolve the above problems, and an object of the present invention is toprovide a forging device and a forging method each of which canmanufacture a forging having a boss portion while achieving reduction incost.

Means for Solving the Problem

One aspect of the present invention to solve the above problems ischaracterized in that: in a forging device including a rotating tablethat rotates around a rotation axis, and a cylindrical shaping roller,the forging device forging a cylindrical workpiece such that an outerperipheral surface of the shaping roller is pressed against an endsurface of the workpiece in a central-axis direction of the workpiecewhile the workpiece is rotated by the rotating table around a centralaxis of the workpiece, the shaping roller is placed apart from therotation axis, and a position of that end of the outer peripheralsurface of the shaping roller which is opposite to a rotation-axis sidein a central-axis direction of the shaping roller is placed at an outerside in a radial direction of the workpiece relative to a position of anouter peripheral surface of the workpiece that has been forged.

According to the above aspect, it is possible to perform diameterexpansion molding to expand the cylindrical workpiece in the radialdirection such that the outer peripheral surface of the shaping rolleris pressed against the end surface of the workpiece in the central-axisdirection of the workpiece while the workpiece is rotated by therotating table around the central axis of the workpiece. Further, sincethe shaping roller is placed apart from the rotation axis of therotating table, a material of the workpiece flows toward therotation-axis side relative to the shaping roller, so that boss moldingto form a boss portion formed by raising a central part of the workpiecein the central-axis direction of the workpiece can be performed. Thus,the diameter expansion molding and the boss molding can be performed atthe same time. This makes it possible to manufacture a forging havingthe boss portion while achieving reduction in cost.

Further, the position of that end of the outer peripheral surface of theshaping roller which is opposite to the rotation-axis side in thecentral-axis direction of the shaping roller is placed at the outer sidein the radial direction of the workpiece relative to the position of theouter peripheral surface of the workpiece that has been forged. Thiscauses such a state where the outer peripheral surface of the shapingroller is pressed against a large area of the end surface of theworkpiece in the central-axis direction of the workpiece, during theforging of the workpiece. This makes it possible to secure accuracy ofthe end surface of the workpiece that has been forged, by the outerperipheral surface of the shaping roller. This can accordingly improvethe accuracy of the end surface of the workpiece that has been forged.

In the forging device, it is preferable that: the forging device includea cylindrical mandrel; a central axis of the mandrel accord with therotation axis; the shaping roller have an inner end surface placed atthe rotation-axis side in the central-axis direction of the shapingroller; and a distance between the central axis of the mandrel and theinner end surface be larger than a radius of the mandrel but smallerthan a radius of the workpiece.

According to the above aspect, by flowing the material of the workpiecebetween the outer peripheral surface of the mandrel and the inner endsurface of the shaping roller, it is possible to form the boss portionhaving a hollow cylindrical shape in the central part of the workpiece.Since the material of the workpiece flows while making close contactwith the outer peripheral surface of the mandrel, it is possible tosecure desired accuracy in an inner peripheral surface of the bossportion by managing accuracy of the outer peripheral surface of themandrel.

It is preferable that the forging device include two shaping rollers.

According to the above aspect, it is possible to shorten a time to forgethe workpiece. Also, the accuracy of the end surface of the workpiece isimproved.

In the forging device, it is preferable that a central axis of theshaping roller be generally perpendicular to the rotation axis.

According to the above aspect, it is possible to simplify a mechanismfor supporting the shaping roller. Particularly, in a case where twoshaping rollers are provided, the two shaping rollers can be integratedwith each other by one shaft member while central axes of the twoshaping rollers accord with each other. This makes it possible tosimplify the mechanism for supporting the two shaping rollers.

Another aspect of the present invention to solve the above problems ischaracterized in that: in a forging method for forging a cylindricalworkpiece, by use of a rotating table that rotates around a rotationaxis, and a cylindrical shaping roller, such that an outer peripheralsurface of the shaping roller is pressed against an end surface of theworkpiece in a central-axis direction of the workpiece while theworkpiece is rotated by the rotating table around a central axis of theworkpiece, the shaping roller is placed apart from the rotation axis,and a position of that end of the outer peripheral surface of theshaping roller which is opposite to a rotation-axis side in thecentral-axis direction of the shaping roller is placed at an outer sidein a radial direction of the workpiece relative to a position of anouter peripheral surface of the workpiece that has been forged.

According to the above aspect, it is possible to perform diameterexpansion molding to expand the cylindrical workpiece in the radialdirection such that the outer peripheral surface of the shaping rolleris pressed against the end surface of the workpiece in the central-axisdirection of the workpiece while the workpiece is rotated by therotating table around the central axis of the workpiece. Further, sincethe shaping roller is placed apart from the rotation axis of therotating table, a material of the workpiece flows toward therotation-axis side relative to the shaping roller, so that boss moldingto form a boss portion formed by raising a central part of the workpiecein the central-axis direction of the workpiece can be performed. Thus,the diameter expansion molding and the boss molding can be performed atthe same time. This makes it possible to manufacture a forging havingthe boss portion while achieving reduction in cost.

Further, the position of that end of the outer peripheral surface of theshaping roller which is opposite to the rotation-axis side in thecentral-axis direction of the shaping roller is placed at the outer sidein the radial direction of the workpiece relative to the position of theouter peripheral surface of the workpiece that has been forged. Thiscauses such a state where the outer peripheral surface of the shapingroller is pressed against a large area of the end surface of theworkpiece in the central-axis direction of the workpiece, during theforging of the workpiece. This makes it possible to secure accuracy ofthe end surface of the workpiece that has been forged, by the outerperipheral surface of the shaping roller. This can accordingly improvethe accuracy of the end surface of the workpiece that has been forged.

In the forging method, it is preferable that: a cylindrical mandrel beused; a central axis of the mandrel accord with the rotation axis; theshaping roller have an inner end surface placed at the rotation-axisside in the central-axis direction of the shaping roller; and a distancebetween the central axis of the mandrel and the inner end surface belarger than a radius of the mandrel but smaller than a radius of theworkpiece.

According to the above aspect, by flowing the material of the workpiecebetween the outer peripheral surface of the mandrel and the inner endsurface of the shaping roller, it is possible to form the boss portionhaving a hollow cylindrical shape in the central part of the workpiece.Since the material of the workpiece flows while making close contactwith the outer peripheral surface of the mandrel, it is possible tosecure desired accuracy in an inner peripheral surface of the bossportion by managing accuracy of the outer peripheral surface of themandrel.

In the forging method, it is preferable that two shaping rollers beused.

According to the above aspect, it is possible to shorten a time to forgethe workpiece. Also, the accuracy of the end surface of the workpiece isimproved.

In the forging method, it is preferable that a central axis of theshaping roller be generally perpendicular to the rotation axis.

According to the above aspect, it is possible to simplify a mechanismfor supporting the shaping roller. Particularly, in a case where twoshaping rollers are provided, the two shaping rollers can be integratedwith each other by one shaft member while central axes of the twoshaping rollers accord with each other. This makes it possible tosimplify the mechanism for supporting the two shaping rollers.

Advantageous Effects of Invention

According to the forging device and the forging method of the presentinvention, it is possible to manufacture a forging having a boss portionwhile achieving reduction in cost.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view illustrating a schematic configuration of aforging device of the present embodiment, and illustrates a state beforeforging is performed on a workpiece.

FIG. 2 is a sectional view illustrating the schematic configuration ofthe forging device of the present embodiment, and illustrates a stateafter the forging is performed on the workpiece.

FIG. 3 is a view to describe a principle to perform diameter expansionmolding and boss molding on the workpiece.

FIG. 4 is a sectional view taken along a line A-A in FIG. 3.

FIG. 5 is a view to describe a conventional technique.

FIG. 6 is a sectional view illustrating a schematic configuration of aforging device of a modification.

FIG. 7 is a sectional view illustrating a schematic configuration of aforging device of a modification.

FIG. 8 is a sectional view illustrating a schematic configuration of aforging device of a modification.

FIG. 9 is a top view of a mandrel in the forging device of themodification illustrated in FIG. 8.

FIG. 10 is a sectional view illustrating a schematic configuration of aforging device of a modification.

FIG. 11 is a sectional view illustrating a schematic configuration of aforging device of a modification.

MODES FOR CARRYING OUT THE INVENTION

The following describes an embodiment of the present invention in detailwith reference to the drawings.

<Description of Forging Device>

Initially described is a configuration of a forging device 1. Here,FIGS. 1 and 2 are each a sectional view illustrating a schematicconfiguration of the forging device 1 of the present embodiment. FIG. 1illustrates a state before forging is performed on a workpiece W, andFIG. 2 illustrates a state after the forging is performed on theworkpiece W. As illustrated in FIGS. 1, 2, the forging device 1 includesa rotating table 10, a mandrel 12, a shaping roller 14, roller movingmeans (not shown), and so on.

The rotating table 10 rotates around a rotation axis L1. Further, therotating table 10 rotates the workpiece W placed on a surface 10 a,around a central axis of the workpiece W.

The mandrel 12 is formed in a cylindrical shape. The mandrel 12 isplaced on the surface 10 a of the rotating table 10 so that a centralaxis of the mandrel 12 accords with the rotation axis L1 of the rotatingtable 10. When the workpiece W is placed on the surface 10 a of therotating table 10, the mandrel 12 is inserted inside an inner peripheralsurface Wa of the workpiece W, and the workpiece W is placed on thesurface 10 a of the rotating table 10 with an outer peripheral surface12 a of the mandrel 12 making contact with the inner peripheral surfaceWa of the workpiece W. This allows the central axis of the workpiece Wto accord with the rotation axis L1 and the central axis of the mandrel12.

The shaping roller 14 is formed in a cylindrical shape. Further, theshaping roller 14 includes an outer peripheral surface 14 a, an innerend surface 14 b, and so on. Here, the inner end surface 14 b is an endsurface on a rotation-axis-L1 side in a central-axis-L2 direction of theshaping roller 14.

In an example illustrated in FIG. 1, two shaping rollers 14 areprovided. The two shaping rollers 14 are placed at respective positionswhose phases are shifted by 180° to each other in a rotation directionof the rotating table 10. The two shaping rollers 14 are integrated witheach other by a shaft 20 in such a state where their central axes L2accord with each other. The shaft 20 is attached to a housing 22 in arotatable state. Because of this, the two shaping rollers 14 integratedwith each other by the shaft 20 rotate integrally around the centralaxes L2 of the shaping rollers 14.

Further, as illustrated in FIG. 1, the shaping roller 14 is placed apartfrom the rotation axis L1. That is, a gap is provided between therotation axis L1 and the inner end surface 14 b of the shaping roller 14(more specifically, an intersection of the inner end surface 14 b withthe central axis L2). A distance δ0 between the rotation axis L1 and theinner end surface 14 b is larger than a radius r of the mandrel 12, butsmaller than a radius R0 of the workpiece W.

Further, the central axis L2 of the shaping roller 14 is generallyperpendicular to the rotation axis L1. More specifically, the centralaxis L2 intersects with the rotation axis L1 at an angle of 90°±10°(that is, 80° to 100°), for example.

Note that materials of the rotating table 10, the mandrel 12, and theshaping roller 14 may be cold working tool steel (SKD11, SKH), cementedcarbide, and the like, for example. Further, the outer peripheralsurface 14 a of the shaping roller 14 is a part that makes contact withthe workpiece W, which will be described later. On this account, it isdesirable that coating be performed on the outer peripheral surface 14 aof the shaping roller 14 so as to maintain a surface state.

Further, the roller moving means is attached to the housing 22. Theroller moving means moves the housing 22 in parallel along arotation-axis-L1 direction of the rotating table 10, so as to move thetwo shaping rollers 14 in parallel to the rotation axis L1. Note thatthe roller moving means is a ball screw, a hydraulic mechanism, or thelike, for example.

Further, the forging device 1 includes a controlling portion (notshown). The controlling portion is constituted by a microcomputer, forexample, and controls driving of the rotating table 10, the rollermoving means, and so on.

<Description of Forging Method>

Next will be described a forging method for forging the workpiece W byuse of the forging device 1, as an operation of the forging device 1having the above configuration.

In the present embodiment, first, the workpiece W having a hollowcylindrical shape is placed on the surface 10 a of the rotating table10. At this time, the mandrel 12 is inserted inside the inner peripheralsurface Wa of the workpiece W so that the central axis of the workpieceW accords with the rotation axis L1 of the rotating table 10. Note thata height H (a length in the rotation-axis-L1 direction) of the mandrel12 is larger than a height h (a length in the rotation-axis-L1direction) of the workpiece W.

Then, the rotating table 10 and the mandrel 12 are rotated around therotation axis L1 (the central axis of the mandrel 12, the central axisof the workpiece W). Hereby, the workpiece W is rotated around therotation axis L1.

Then, the shaping roller 14 is moved toward the workpiece W by theroller moving means. Then, the outer peripheral surface 14 a of theshaping roller 14 is pressed against an end surface Wb of the workpieceW (an end surface thereof at a shaping-roller-14 side in thecentral-axis direction of the workpiece W), so that the shaping roller14 makes contact with the workpiece W. Here, as described above, theworkpiece W is being rotated around the rotation axis L1. Because ofthis, when the shaping roller 14 makes contact with the workpiece W asdescribed above, the shaping roller 14 rotates following the workpieceW. That is, the shaping roller 14 rotates around the central axis L2.

Further, the shaping roller 14 is moved toward the workpiece W by theroller moving means. This causes a pressure to be applied to the endsurface Wb of the workpiece W from the shaping roller 14, so that theworkpiece W expands outwardly in a radial direction of the workpiece W.Hereby, diameter expansion molding is performed on the workpiece W.

Further, in the present embodiment, the distance δ0 between the rotationaxis L1 of the rotating table 10 (the central axis of the workpiece W)and the inner end surface 14 b of the shaping roller 14 is larger thanthe radius r of the mandrel 12, but smaller than the radius R0 (seeFIG. 1) of the workpiece W before the workpiece W is forged and a radiusR1 (see FIG. 2) of the workpiece W after the workpiece W is forged.Hereby, at the time when the workpiece W is forged and after theworkpiece W is forged, the shaping roller 14 is separated from themandrel 12, as illustrated in FIG. 2. More specifically, the outerperipheral surface 12 a of the mandrel 12 is separated from the innerend surface 14 b of the shaping roller 14 by a distance δ1, so that agap is provided between the outer peripheral surface 12 a of the mandrel12 and the inner end surface 14 b of the shaping roller 14. Because ofthis, when a pressure is applied to the end surface Wb of the workpieceW from the shaping roller 14 as described above, a radially inner partof the workpiece W is raised toward a shaping-roller-14 side in therotation-axis-L1 direction, as illustrated in FIG. 2. Hereby, a bossportion Wc raised in the central-axis direction of the workpiece W isformed at a central part of the workpiece W. Thus, boss molding isperformed on the workpiece W.

Here, the following more specifically describes how the diameterexpansion molding and the boss molding are performed on the workpiece W.At the time when the workpiece W is forged, the shaping roller 14revolves around the rotation axis L1 of the rotating table 10 asillustrated in FIG. 3, when viewed from the workpiece W. At this time,due to movement of an intersection between the workpiece W and theshaping roller 14, a material of the workpiece W flows toward anouter-peripheral-surface-Wd side of the workpiece W so that the materialis scraped off, as illustrated in FIG. 4, and also flows toward arotation-axis-L1 side (a mandrel-12 side). When the material of theworkpiece W flows toward the outer-peripheral-surface-Wd side of theworkpiece W, the diameter expansion molding to expand the workpiece W inthe radial direction of the workpiece W is performed. Further, when thematerial of the workpiece W flows toward the rotation-axis-L1 side (themandrel-12 side), the material of the workpiece W flows to thecentral-axis direction of the workpiece W along the outer peripheralsurface 12 a of the mandrel 12. Hereby, the boss molding to form theboss portion Wc is performed.

As described above, in the present embodiment, it is possible to performthe diameter expansion molding and the boss molding on the workpiece Wat the same time.

Here, in a conventional technique (e.g., Japanese Patent ApplicationPublication No. 61-144232 (JP 61-144232 A), at the time when a workpieceW0 is forged and after the workpiece W0 is forged, a position of anouter end 104 on a shaping surface 102 of a shaping roller 100 is placedat an inner side in a radial direction of the workpiece W relative to aposition of an outer periphery W0 b of the workpiece W0, as illustratedin FIG. 5. This causes such a state that the shaping surface 102 of theshaping roller 100 is pressed against only part of an end surface W0 aof the workpiece W0 in the radial direction of the workpiece W0, so thataccuracy of the end surface W0 a of the workpiece W0 that has beenforged might decrease.

In contrast, in the forging device 1 of the present embodiment, aposition of that outer end 14 c of the outer peripheral surface 14 a ofthe shaping roller 14 which is opposite to the rotation-axis-L1 side inthe central-axis-L2 direction is placed at an outer side in the radialdirection of the workpiece W relative to a position of the outerperipheral surface Wd of the workpiece W that has been forged, asillustrated in FIG. 2. This causes such a state where the outerperipheral surface 14 a of the shaping roller 14 is pressed against alarge area of the end surface Wb of the workpiece W in the radialdirection of the workpiece W, from the beginning of the forging of theworkpiece W to the end of the forging. This makes it possible to secureaccuracy of the end surface Wb of the workpiece W that has been forged,by the outer peripheral surface 14 a of the shaping roller 14. Thisaccordingly improves accuracy of the end surface Wb of the workpiece Wthat has been forged.

Further, in comparison with conventional die forging (forging using amolding die), the forging device 1 can perform the diameter expansionmolding and the boss molding at a low load.

Further, in the present embodiment, since the material of the workpieceW flows while making close contact with the mandrel 12 from thebeginning of molding, accuracy of an inside diameter of the workpiece Wthat has been forged can be easily secured.

Note that such an example in which only one shaping roller 14 isprovided can be considered as a modification.

Further, as another modification, such an example in which a mandrel 12is provided separately from a rotating table 10 can be considered, asillustrated in FIG. 6. Further, as illustrated in FIG. 7, such anexample in which a surface 10 a of a rotating table 10 is formed as aninclined surface, and an outer peripheral surface 14 a of a shapingroller 14 is formed to be inclined relative to a central axis L2 can bealso considered. Further, as illustrated in FIGS. 8, 9, splines may beformed on an outer peripheral surface 12 a of a mandrel 12. This makesit possible to form a boss portion Wc while forming splines on an innerperipheral surface Wa of a workpiece W. Further, as illustrated in FIG.10, such an example in which a surface 10 a of a rotating table 10 isformed to have a waveform shape.

Further, as another modification, a forging device that does not includea mandrel 12 can be considered, as illustrated in FIG. 11. At this time,a workpiece W that has not been forged yet is formed in a solidcylindrical shape. Note that FIGS. 6 to 8, 10, and 11 partiallyillustrate a forging device.

Further, as a modification, such an example in which a central axis L2of a shaping roller 14 intersects with a rotation axis L1 of a rotatingtable 10 at an angle of 45° to 90° can be considered.

<Effect of Present Embodiment>

In the present embodiment, in the forging device 1 which includes therotating table 10 that rotates around the rotation axis L1, and thecylindrical shaping roller 14, and which forges the cylindricalworkpiece W such that the outer peripheral surface 14 a of the shapingroller 14 is pressed against the end surface Wb of the workpiece W inthe central-axis direction of the workpiece W while the workpiece W isrotated by the rotating table 10 around the central axis of theworkpiece W, the shaping roller 14 is placed apart from the rotationaxis L1, and the position of that outer end 14 c of the outer peripheralsurface 14 a of the shaping roller 14 which is opposite to therotation-axis-L1 side in the central-axis-L2 direction of the shapingroller 14 is placed at the outer side in the radial direction of theworkpiece W relative to the position of the outer peripheral surface Wdof the workpiece W that has been forged.

As such, the diameter expansion molding to expand the cylindricalworkpiece W in the radial direction can be performed such that the outerperipheral surface 14 a of the shaping roller 14 is pressed against theend surface Wb of the workpiece W in the central-axis-L2 direction ofthe workpiece W while the workpiece W is rotated by the rotating table10 around the central axis of the workpiece W. Further, since theshaping roller 14 is placed apart from the rotation axis L1 of therotating table 10, the material of the workpiece W flows toward therotation-axis-L1 side relative to the shaping roller 14, so that theboss molding to form the boss portion Wc formed by raising a centralpart of the workpiece W in the central-axis direction of the workpiece Wcan be performed. Thus, the diameter expansion molding and the bossmolding can be performed at the same time. This makes it possible tomanufacture a forging having the boss portion Wc while achievingreduction in cost.

Further, the position of that outer end 14 c of the outer peripheralsurface 14 a of the shaping roller 14 which is opposite to therotation-axis-L1 side of the rotating table 10 in the central-axis-L2direction of the shaping roller 14 is placed at the outer side in theradial direction of the workpiece W relative to the position of theouter peripheral surface Wd of the workpiece W that has been forged.This causes such a state where the outer peripheral surface 14 a of theshaping roller 14 is pressed against a large area of the end surface Wbof the workpiece W, in the central-axis direction of the workpiece W,during the forging of the workpiece W. This makes it possible to secureaccuracy of the end surface Wb of the workpiece W that has been forged,by the outer peripheral surface 14 a of the shaping roller 14. This canaccordingly improve the accuracy of the end surface Wb of the workpieceW that has been forged.

Further, it is preferable that: the forging device 1 include thecylindrical mandrel 12; the central axis of the mandrel 12 accord withthe rotation axis L1 of the rotating table 10; the shaping roller 14have the inner end surface 14 b placed at the rotation-axis-L1 side inthe central-axis-L2 direction of the shaping roller 14; and the distanceδ1 between the central axis of the mandrel 12 and the inner end surface14 b be larger than the radius of the mandrel 12, but smaller than theradius of the workpiece.

Hereby, by flowing the material of the workpiece W between the outerperipheral surface 12 a of the mandrel 12 and the inner end surface 14 bof the shaping roller 14, it is possible to form the boss portion Wchaving a hollow cylindrical shape in the central part of the workpieceW. Since the material of the workpiece W flows while making closecontact with the outer peripheral surface 12 a of the mandrel 12, it ispossible to secure desired accuracy on an inner peripheral surface ofthe boss portion Wc by managing accuracy of the outer peripheral surface12 a of the mandrel 12.

Further, when the forging device 1 includes two shaping rollers 14, itis possible to shorten a time to forge the workpiece W. Also, theaccuracy of the end surface Wb of the workpiece W is improved.

Further, in the forging device 1, the central axis L2 of the shapingroller 14 is generally perpendicular to the rotation axis L1 of therotating table 10. This makes it possible to simplify a mechanism forsupporting the shaping roller 14. Particularly, in a case where twoshaping rollers 14 are provided, the two shaping rollers 14 can beintegrated with each other by one shaft 20 while central axes of the twoshaping rollers 14 accord with each other. This accordingly makes itpossible to simplify the mechanism for supporting the two shapingrollers 14. Accordingly, the two shaping rollers 14 can be easilyhandled. Further, a force that can be added to the workpiece W from theshaping rollers 14 can be increased. Also, rigidity of the shapingrollers 14 can be obtained.

Note that the above embodiment is merely an example, and does not limitthe present invention at all. It goes without saying that the presentinvention can be altered or modified variously within a range which doesnot deviate from the gist of the present invention.

INDUSTRIAL APPLICABILITY

A forging manufactured by the forging device 1 and the forging method ofthe present invention is suitable for a power transmission component.For example, the forging is most suitable for steel components used forpower transmission, such as a gear wheel and a shaft used in anautomobile, a construction vehicle, a construction machine, and thelike, and particularly, a transmission gear wheel of an automobile and asheave of CVT.

DESCRIPTION OF THE REFERENCE NUMERALS

-   1 forging device-   10 rotating table-   10 a surface-   12 mandrel-   12 a outer peripheral surface-   14 shaping roller-   14 a outer peripheral surface-   14 b inner end surface-   14 c outer end-   20 shaft-   22 housing-   L1 rotation axis-   L2 central axis-   W workpiece-   Wa inner peripheral surface-   Wb end surface-   Wc boss portion-   Wd outer peripheral surface-   H height (of mandrel)-   h height (of workpiece)-   r radius (of mandrel)-   R0 radius (of workpiece that has not been forged)-   R1 radius (of workpiece that has been forged)-   δ0 distance-   δ1 distance

1. A forging device comprising: a rotating table that rotates around arotation axis, and a cylindrical shaping roller, wherein the forgingdevice forges a cylindrical workpiece such that an outer peripheralsurface of the shaping roller is pressed against an end surface of theworkpiece in a central-axis direction of the workpiece while theworkpiece is rotated by the rotating table around a central axis of theworkpiece, the shaping roller is placed apart from the rotation axis;and a position of that end of the outer peripheral surface of theshaping roller which is opposite to a rotation-axis side in acentral-axis direction of the shaping roller is placed at an outer sidein a radial direction of the workpiece relative to a position of anouter peripheral surface of the workpiece that has been forged.
 2. Theforging device according to claim 1, further comprising: a cylindricalmandrel, wherein: a central axis of the mandrel accords with therotation axis; the shaping roller has an inner end surface placed at therotation-axis side in the central-axis direction of the shaping roller;and a distance between the central axis of the mandrel and the inner endsurface is larger than a radius of the mandrel but smaller than a radiusof the workpiece.
 3. The forging device according to claim 1, whereintwo shaping rollers are provided in the forging device.
 4. The forgingdevice according to claim 1, wherein: a central axis of the shapingroller is generally perpendicular to the rotation axis.
 5. A forgingmethod for forging a cylindrical workpiece, by use of a rotating tablethat rotates around a rotation axis, and a cylindrical shaping rollercomprising: rotating the workpiece around a central-axis direction ofthe workpiece by rotating the table, pressing an outer peripheralsurface of the shaping roller against an end surface of the workpiece ina central-axis direction of the workpiece, wherein the shaping roller isplaced apart from the rotation axis; and a position of that end of theouter peripheral surface of the shaping roller which is opposite to arotation-axis side in a central-axis direction of the shaping roller isplaced at an outer side in a radial direction of the workpiece relativeto a position of an outer peripheral surface of the workpiece that hasbeen forged.
 6. The forging method according to claim 5, wherein: acylindrical mandrel is used; a central axis of the mandrel accords withthe rotation axis; the shaping roller has an inner end surface placed atthe rotation-axis side in the central-axis direction of the shapingroller; and a distance between the central axis of the mandrel and theinner end surface is larger than a radius of the mandrel but smallerthan a radius of the workpiece.
 7. The forging method according to claim5, wherein: two shaping rollers are used.
 8. The forging methodaccording to claim 5, wherein: a central axis of the shaping roller isgenerally perpendicular to the rotation axis.